1. Field of the Invention
The present invention relates to polarity indicators and more specifically to a polarity indicator located on a battery and which upon contact of connecting means of an external direct current (D.C.) supply gives out a visual signal as to the polarity of the connecting means relative to the polarity of the battery.
Modern automobiles, vehicles and many stationary power sources commonly utilize a D.C. electrical system to start the respective engines and to operate associated equipments. These electrical systems generally rely upon and utilize storage batteries to supply the necessary electric current.
Although such systems are generally reliable, it is often necessary or desirable to supply electrical current to the system from an external source to supplement the output of the storage battery, such as when the storage battery is in a discharged or dead condition. For example, when storage batteries fail to start a vehicle, it is common practice to use jumper cables extending from the battery terminals of an able vehicle to the battery terminals of a disabled vehicle to temporarily aid in starting the disabled vehicle. Such jumber cables have spring clamps commonly known as alligator clips adapted to grip battery terminals, at each end of each of a pair of electrical conductors that have an insulation jacket.
The use of jumper cables is a recognized hazard. The greatest danger involves the incorrect connection of the positive and negative terminals of the battery. The depleted battery and the electrical supply must indeed be connected with their polarities matched or in other words, they must be connected so that the positive terminal of the battery of the able vehicle is connected with the positive terminal of the disabled vehicle's battery and similarly for the negative terminals. If the polarities are mismatched, the result will be arcing, extremely large current flow, dangerous overheating of the cables and battery, splashing of acid from the battery and possible damage to the battery and supply. Damage to the electrical apparatus of the vehicle may also occur.
The potential danger has become particularly important with the advent of alternator systems, transistor radios, voltage regulators and newer ignition systems which can easily be burned out by an improper connection. The alternator tends to be the most susceptible of all the elements of the electrical system to the improper connection and contains diodes that fail very rapidly at currents above rated values.
Another danger involves battery explosion due to sparks igniting hydrogen gas.
Indeed, the batteries produce hydrogen when charging and sparks from the nearly jumper to battery connection can set off an explosion.
The batteries sometimes burst from the explosion and spatter battery acid on bystanders.
Although this type of explosion can also occur when the connection is correctly made, it becomes increasingly probable when the polarities are mismatched.
Accordingly, numerous patents disclose devices designed to minimize the risks of inverting the polarity during the connection of booster cables.
Most of these devices such as the one disclose in U.S. Pat. No. 4,217,534 comprise an indicator interposed between a set of jumber cables and providing a visual and/or aural indication of relative battery polarity as well as a safety circuit to prevent electrical connection when the polarities are reversed. Such systems are integrated with the booster cables. Such devices therefore present the disadvantage of being potentially lost or stolen. Furthermore, they are relatively complex and therefore subject to breakdown and relatively expensive to manufacture.
Another type of device includes an arrangement connected to the battery of each car. The arrangement includes a special plug receptacle designed so that the conductor can only be connected thereto in one way. Examples of such devices are disclosed in U.S. Pat. Nos. 3,466,453, 4,079,304, 4,157,492 and 4,759,728.
Since this type of device is usually attached to the vehicle or the battery, they cannot be lost as was the case with the previously mentioned device.
However, they require the use of a special plug and plug receptacle and therefore cannot be used with conventional booster cables.
The present invention is intended to circumvent the above-mentioned disadvantages.
Accordingly, the invention relates to a polarity indicator which can be readily attached to conventional batteries and which will give a visual indication as to the correct orientation of the booster cables prior to the actual connection of the gripping jaws to the terminals of the battery by a mere contact with the poles of the indicator.
The invention also relates to a polarity indicator which will conform to conventional forms of manufacturing, be of simple construction and easy to use as to provide a polarity indicator which will be economically feasable, long lasting and relatively trouble free in operation.